Getting a good seal is unarguably one of the most important things you can do to ensure the quality of forages in bunker silos and drive-over piles.
“After hybrid selection and packing density, it’s the third most important thing you do when you manage a bunker or pile,” says Keith Bolsen, a professor emeritus of ruminant nutrition at Kansas State University.
However, the industry as a whole could stand to do a better job on sealing bunkers and piles.
Each year, losses due to unsealed or poorly sealed silage top a quarter billion dollars, says Bolsen, who since retiring in 2003 has continued to operate a silage-management consulting business with his wife, Ruthie.
“We simply cannot afford to cut corners because we have to live with the consequences all year long,” Bolsen says. “It’s a very important final step in preparing your silage for storage and feed out.”
Here are the latest recommendations to focus on when sealing bunkers and silage piles.
Know your plastic’s oxygen barrier rate
Larry Burrows knows something about traditional “5-mil” plastic coverings that might surprise you — they can breathe.
“When you look at the 5-mil… underneath a microscope, you can see it’s porous. It will breathe, so-to-speak,” says Burrows, an independent dairy nutritionist with Progressive Dairy Solutions Inc., in Kimberly, Idaho.
Bolsen also has been met with skepticism when he tells producers that oxygen penetrates traditional black-on-white polyethylene plastic.
He relates an observation made by a producer during a meeting. This producer questioned how oxygen could possibly go through the plastic when he’s seen it hold water.
“I said, ‘Oxygen is a smaller molecule than water. It can move through it at a slow rate,’” Bolsen says.
Even slow infiltration can cause damage to silage quality, and is why both Bolsen and Burrows now recommend using plastic film that provides a barrier against oxygen.
Pay attention to the term “oxygen transfer rate” or “OTR,” Burrows says. Ideally, you’ll want to use a product that provides as close to 100 percent oxygen barrier protection as possible. When examining a commercial product, be sure to ask for its oxygen transmission rate and any independent lab test results that back up the product’s oxygen-barrier claims.
Use two layers
Even with the advent of oxygen-barrier film, you still need to cover the silage with two layers — the first layer designed to prevent oxygen infiltration, and the second to protect the silage from damaging ultraviolet light.
An example of this would be to use an oxygen-barrier film, which can be clear or transparent, followed by a standard 5- or 6-mil black-on-white polyethylene sheet.
The first layer “clings” — think household plastic wrap — to the silage surface, Burrows says. It also likes to cling to itself, so be mindful of this when working with the material.
“Go back over the top of that with the 5-mil,” he says.
You might be wondering if using two layers of black-on-white polyethylene does the same job.
Bolsen says this approach — which he recommended for many years — does not offer the same level of protection as a two-layer approach using an oxygen-barrier film.
“We’re still going to have some surface spoilage over time that’s going to need to be pitched, and it’s simply too dangerous today to even think about pitching surface spoilage.”
(Please see “Ditch the pitch” at below.)
Line the sides, too
It’s not enough just to cover and seal the top, Burrows says. Also bring the plastic down the sides of the forage.
For step-by-step directions on how to line the sidewalls of a bunker, type “Secure your sidewalls” into the “Search” box.
If you’re not ensiling and sealing your forages correctly, “then you’re certainly losing nutrients and the quality of your forages,” Burrows says. “The price of feed is so high, you can’t afford to replace those.”
To learn more about minimizing surface-spoiled silage in bunker silos and drive-over piles, type “10 spoilage stoppers” into the “Search” box.